A dam leak at a molybdenum mine in northeastern China’s Heilongjiang province is at risk of contaminating the water supply of nearby residents, local authorities said at a press conference Monday.

The leak occurred Saturday at a tailings pond of the Yichun Luming Mining Co. Ltd., located more than 200 kilometers from the provincial capital of Harbin. Tailings are usually a liquid slurry consisting of unwanted ground minerals separated by ore extraction.

Authorities said that about 2.5 million cubic meters of wastewater had leaked into the province’s Yijimi River, a surface water source for some 300,000 people in Tieli City. The city suspended its surface water intake on Sunday and switched to extracting groundwater.

Molybdenum is a metal used in making steel and other alloys. It is unclear if excessive exposure to molybdenum could present health risks for humans. (Image: From @新华视点 on Weibo)